True or false: ultrasounds are totally safe

Ultrasound scans are routinely offered throughout pregnancy to monitor the health, development and growth of baby in the womb. Typically offered at 12 and 20 weeks, you may also be offered additional scans before and after these points. Additionally, private ultrasound scans outside the NHS have gained popularity, with private companies offering 3D scans and reassurance ultrasound scans.

Ultrasound uses high frequency sound waves which are transmitted through the body, and bounce back when they hit differing density body parts, creating a black and white image on screen. The ultrasound scans in pregnancy check things like the growth of baby, their bones, organ function, umbilical cord blood flow and more.

Is ultrasound safe?

The truth is, we don’t know. Yes millions of babies are scanned using ultrasound, but studies investigating whether there are any side effects of ultrasound use are limited. There is no doubt that ultrasound use identifies problems with unborn babies and is responsible for saving many lives, but we do not know what potential harm ultrasound may cause.

Obstetrician Ian Donald was responsible for discovering ultrasound for medical purposes after he spotted that the machine that dockyard workers were using to detect cracks in the hull of a submarine could be used to detect tumours. It then became mainstream in medical use.

What does the research say?

Studies are limited, but there are some small studies with concerning results.

One small study in 1990 found that people given ultrasounds who were at risk of preterm labour were twice as likely to go in to preterm labour than those at risk who were offered pelvic exams instead (52% vs 25%) (R P Lorenz et al. Am J Obstet Gynecol. 1990)

Two other larger studies both found that there were higher instances of perinatal death in groups exposed to ultrasound than not (Saari-Kemppainen et al. 1990 & Davies JA et al. 1992)

Additionally, one study looking at pregnant Physiotherapists using ultrasound on patients therapeutically found the physiotherapists themselves were at risk:

“Exposure to ultrasound and shortwaves showed about threefold odds ratios for spontaneous abortions occurring after the 10th week of gestation. Deep heat therapies together, and shortwaves alone, were associated significantly with congenital malformations” Taskinen H. et al. Effects of ultrasound, shortwaves, and physical exertion on pregnancy outcome in physiotherapists. J Epidemiol Commun Health, 1990

As with everything in maternity care, the key takeaway is informed choice. On balance, most people will opt to consent to ultrasound scans, weighing the lack of evidence against scans, and the wealth of evidence showing the benefits they bring, but knowing that they may not be risk free may lead to a consideration of whether multiple or scans which are not of medical benefit are necessary.It is also important to know that scans are not compulsory and as with everything else in pregnancy and birth, you can decline them if you prefer.


  1. Lorenz RP et al. Randomized prospective trial comparing ultrasonography and pelvic examination for preterm labor surveillance. Am J Obstet Gynecol, 1990; 162 (6): 1603-10

  2. Saari-Kemppainen et al. Ultrasound screening and perinatal mortality: controlled trial of systematic one-stage screening in pregnancy. Lancet, 1990; 336 (8712): 387-91

  3. Davies JA et al. Randomised controlled Doppler ultrasound screening of placental perfusion during pregnancy. Lancet, 1992; ii: 1299-303

  4. Taskinen H. et al. Effects of ultrasound, shortwaves, and physical exertion on pregnancy outcome in physiotherapists. J Epidemiol Commun Health, 1990; 44 (3): 196-201

  5. AIMS: Ultrasound unsound Beverley A Lawrence Beech & Jean Robinson

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